1. Field of the Invention
The present invention relates to a bushing for leading an electrical connector through a wall or the like, comprising an intermediate flange for attachment in the wall, two metallic end flanges arranged on either side of the intermediate flange and two hollow insulators clamped between the intermediate flange and the end flanges, and a bushing conductor running through the whole bushing.
2. The Prior Art
From Swedish Patent No. 90 977, for example, it is known, in such a bushing, to let a central bushing conductor together with the end flanges serve as a device for clamping together the above-mentioned bodies of insulating material.
When the bushing is mounted, the bushing conductor is given such a prestress large enough to fix the main parts of the bushing by means of frictional forces. Since, for example, ceramic material has a very low coefficient of thermal expansion in comparison with metal, the bushing conductor will have a greater extension with increasing temperature than the insulators which are pressed against the middle flange, which may have the result that the clamping force becomes too low at increasing temperature. With decreasing temperature, there may be a risk that the bushing conductor will be stretched beyond the range of elastic tension and will acquire a permanent plastic extension. This may have the result that the clamping force becomes even lower in the case of renewed heating.